知识点
1.scroll家族和offset家族的结合运用
2.当nav的offsetTop大于屏幕卷去高度的时候，进行吸顶
3.添加一个固定类，如果满足条件，为nav加类名
运行效果
滚动页面时，保证导航栏吸顶
代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title></title>
<style>
*{margin: 0;padding: 0;list-style: none;border:none}
img{vertical-align: top;width: 100%;}
section{width: 70%;margin: 0 auto;}
.nav{position: fixed;left: 0;top: 0;width: 100%}
</style>
</head>
<body>
<header id="head">
<img src="images/top.png" alt="">
</header>
<nav id="nav">
<img src="images/nav.png" alt="">
</nav>
<section>
<img src="images/body01.png" alt="">
<img src="images/body02.png" alt="">
</section>
<script src="../../MyTools/MyTools.js"></script>
<script>
window.addEventListener('load',function (ev) {
// 1. 求出头部高度
var navTopHeight = myTool.$('nav').offsetTop;
// 2. 监听页面滚动
window.addEventListener('scroll',function (ev1) {
var scrollTopHeight = myTool.scroll().top;
// 2.1 判断
if(scrollTopHeight >= navTopHeight){
myTool.addClassName(myTool.$('nav'),'nav')
}else{
myTool.removeClassName(myTool.$('nav'),'nav');
}
})
})
</script>
</body>
</html>
